What each type of maintenance means
Corrective maintenance takes place after an asset fails or shows a deviation. It can be planned (the repair is scheduled for a suitable time) or emergency (operations have already been affected).
Preventive maintenance is scheduled by time or usage, regardless of whether the asset has failed: inspections, lubrication, filter replacements and adjustments follow a defined calendar.
Predictive maintenance decides on intervention based on the actual condition of the asset, measured through inspection, thermography, vibration analysis, monitoring of electrical parameters or other techniques. The intervention happens when the data indicates a need, not just when the calendar says so.
Why it is not about choosing just one
Treating the three as mutually exclusive options leads to two common extremes: running almost entirely on corrective maintenance, with unexpected downtime, or applying preventive maintenance to everything, at a high cost for assets that do not justify that level of care.
The useful question is not which type is best, but which strategy makes sense for each asset, considering the impact of a failure and the cost of preventing it.
Asset criticality as the criterion
Classifying assets by criticality structures the decision. A simple approach is to combine the impact of a failure on operations, the probability of occurrence, the existence of redundancy and the time needed to restore the asset.
- High-criticality assets, such as emergency power generation, main electrical switchboards and essential HVAC systems: a combination of rigorous preventive maintenance and predictive techniques.
- Medium-criticality assets: a well-defined preventive plan, with inspections that may point to the need for monitoring.
- Low-criticality assets: planned corrective maintenance is usually the most cost-effective option, provided the failure does not pose a safety risk.
Regulatory reference
In Brazil, the ABNT NBR 5674 standard sets requirements for building maintenance management systems. It treats maintenance as a system, with planning, records and control, rather than as a sequence of isolated repairs.
How to structure it in practice
- Build an asset inventory, with location, type and manufacturer information.
- Classify each asset by criticality.
- Define the strategy for each asset class (planned corrective, preventive, predictive).
- Record work orders and intervention history, preferably in a maintenance management system.
- Track indicators such as preventive plan compliance, share of emergency corrective work and mean time to repair.
- Review the plan periodically based on failure history.
Frequently asked questions
Is predictive maintenance always the best option?
No. It requires instruments, data collection and analysis, which is only justified when a failure has a significant impact. For low-criticality assets, planned corrective maintenance may be more appropriate.
Where should we start when there is no maintenance plan?
With the asset inventory and the criticality classification. Without knowing what exists and what is critical, any plan tends to be generic.
What is the difference between planned and emergency corrective maintenance?
In planned corrective maintenance, the deviation is identified before a complete failure and the repair is scheduled. In emergency corrective maintenance, the asset has already stopped and the repair must be done immediately, which usually costs more and affects operations.